KANSAS CITY, Mo. — Mariano Rivera insisted on standing on his torn ACL as he hobbled out of the trainer’s room toward a square table surrounded by tape recorders and microphones.

The pain was more mental than physical now, he admitted, though the grim, likely season-ending diagnosis that came late last night had not fully set in. The closer started his afternoon at the Kauffman Stadium doing what made him tick for the last 18 years — shagging fly balls in the outfield to warm up during batting practice.

Then came the trip, the knee that buckled between the outfield grass and the warning track, the moments spent writhing in pain as trainers bolted to his side, the ride to the hospital for the MRI and the news from Kansas City’s lead team physician that he suffered an injury that typically requires a year’s worth of rehabilitation. Rivera also revealed there was some meniscus damage to the knee.

And then came late last night when Rivera, 42, had to face questions regarding his future. He had hinted during spring training this could be his last season. But the man who made his living finishing things, the one who could retire comfortably as Major League Baseball’s all-time saves leader, was not sure if he was ready to give up a month into the 2012 season.

“At this point, I don’t know,” he said, holding back tears. “At this point, I don’t know. I’ll have to face this first.”

Rivera said he would not return to New York today. Instead, he will stay with the Yankees all weekend and spend time with his teammates.

“I don’t want to have it any other way, if I’m going to have it happen like that, well at least it happened doing what I love to do and shagging (fly balls), I love to do,” Rivera said. “If I had to do it all over again, I would do it again no hesitation. There are reasons why it happens, you have to take it the way it is.

“Now, we just have to fight.”

In a silent Yankees locker room a few players lingered eating barbecue though none were talking. There are plenty of questions — which one of them will fill Rivera’s role on the field and which will take it over in the clubhouse — though no answers were readily available.

Manager Joe Girardi, who hustled from behind home plate to aid Rivera in the outfield yesterday afternoon, knew it was grim the moment he helped lift his closer off the ground and into a John Deere groundskeeper’s cart.

“My thought is, he’s got a torn ligament,” he said.

“This is bad, there’s no question about it,” he added. “This is not what you come to Kansas City for to hear, but good teams find a way to overcome things.”

He said that he would sleep on a decision to name the next closer, though David Robertson would have stepped in had there been a save situation last night.

“You’ve all seen Mo run around for – how long has be been here for, the last 40 years?” Girardi said. “He’s been doing it, and no one has ever said a word. That’s part of who he is and no one is ever going to take that away from him. He may not be the same guy, he may not be the same pitcher, but as I said, you can fall off a curb or down stairs.

“I saw a guy pull a rib cage putting a kitchen together for his daughter. These things happen.”

Derek Jeter, who played with Rivera for the better part of two decades, was not prepared to say anything other than why he expected his friend to return and pitch this season.

Alex Rodriguez, who mouthed the words “Oh my God” from home plate as he saw Rivera crumble on the warning track, asked not to discuss it. He did not want to replay the horrid fall.

“It’s hard to talk about it tonight, Mo means so much to us on a personal level,” he said.

Robertson, suspected by many to be Rivera’s heir, would go nowhere near the thought.

“It’s just a miserable feeling to see it,” he said. “I didn’t think it was that bad, I was hoping maybe he’d caught it funny or maybe he’d sprained it or something. But coming in here after the game and finding out the news, it’s the worst news we could have gotten.”

And CC Sabathia summed it up best.

Around them were a roster full of players that had to stand up to the pain, like Rivera did late last night.

“It’s tough,” Sabathia said. “We just need to do whatever we can to step up — try to fill the void of the best closer to ever play baseball. Obviously, it’s going to be real tough.”